This invention relates to a circuit breaker in which the circuit breaking is achieved by separating a movable contact of a rotatable movable contact member from a stationary contact of a stationary contact member.
While circuit connecting or breaking is achieved in a circuit breaker by contacting and separating a movable contact of a movable contact member with respect to a stationary contact of a stationary contact member, an electric arc is generated between the separated movable contact and the stationary contact during the circuit breaking because of a voltage applied to the circuit. Therefore, in the circuit breaking operation, how quickly the arc can be extinguished is an important concern. In a conventional circuit breaker in which the movable contact and the stationary contact are brought into contact or separated by rotating the movable contact member, arc extinguisher plates are disposed in the vicinity of the arc generating position in order to extinguish the arc.
FIGS. 16a and 16b are views showing the conventional circuit breaker arrangement in which the movable contact member is rotated for circuit interruption, FIG. 16a being a perspective view and FIG. 16b being a cross sectional view taken along the line XVIbxe2x80x94XVIb of FIG. 16a and in a plane perpendicular to the bottom surface of the circuit interrupter. In these figures, 101 is a vessel, 102 is a cover placed over the vessel 101. The cover 102 does not retain a high pressure within the cover so that the inner gas is permitted to flow outside.
103 is a movable contact member rotatably attached to a mechanism unit 107 and has a movable contact 103a, 104 is a stationary contact member secured to the vessel 101 and has a stationary contact 104a capable of being contacted by and separated from the movable contact 103a, 105a and 105b are terminals of the stationary contact member 104, 106 are arc extinguishing plates disposed in the vicinity of the arc generating area and 107 is the mechanism unit for rotating the movable contact member 101, which mechanism portion includes a handle 107a for manual operation. 108 is an exhaust port formed in the cover 102 and 109 is a relay unit for detecting an abnormal current and causes the operation of the mechanism unit 107.
In the conventional circuit breaker as above described, as shown in FIGS. 16a and 16b, the electrical connection between the movable contact 103a and the stationary contact 104a are established by being brought into contact with each other, so that an electric current flows through the respective terminals 105a and 105b. 
On the other hand, in order to interrupt the electric current flowing through the terminals 105a and 105b, the mechanism unit 107 is operated by the manual operation through the handle 107a or by an automatic operation caused by a current higher than the rated current, whereby the operating mechanism unit 107 is operated to rotate the movable contact member 103 to cause the movable contact 103a to separate from the stationary contact 104a. At this time, an electric arc is generated between the movable contact 103a and the stationary contact 104a. This arc is elongated by rotational motion of the movable contact member 103 an electromagnetic force generated by the current flowing between the movable contact member 103 and the stationary contact member 104 and, thereafter, the arc is divided and quenched by the arc extinguisher plates 106 extinguished. After this, the movable contact member 103 is held in an open state in which it is separated from the stationary contact 104.
During the interruption in the conventional circuit breaker, the arc is elongated by the rotational motion of the movable contact member 103 and this elongated arc is divided and quenched by the arc extinguisher plates 106, so that the interrupting capability is limited by the number of the arc extinguisher plates 106 and the maximum separation distance of the movable contact member 103 or the size of the arc extinguishing chamber.
Also, although an exhaust port 108 is provided at one side within the arc extinguishing chamber in order to exhaust pressurized arc gas generated upon the arc occurrence, since the conventional circuit breaker does not have sufficient gas-tightness of the vessel, the pressurized arc gas (hereinafter referred to as pressurized gas) is exhausted without being utilized in arc extinction through the spaces defined in the mechanism unit and between the relay unit, the vessel, the cover and the like.
Further, while the arc gas contains gases that are effective for the arc extinction, they are not effectively utilized and the arc extinguishing capability is subjected to limitation by the number of the arc extinguishing plates 106 and the maximum separation distance of the movable contact member 103 or the volume of the arc extinguishing chamber.
The present invention has been made to solve the above problem and has as its object the provision of a compact circuit breaker of a high arc extinguishing capability by utilizing a pressurized gas generated upon the arc occurrence.
Another object is to provide a compact circuit breaker of a high arc extinguishing capability by generating and utilizing a gas effective for arc extinction generated upon the arc occurrence and utilizing.
The circuit breaker according to the present invention comprises a stationary contact member having a stationary contact, a movable contact member having at one end a movable contact capable of contacting with and separating from the stationary contact and having at the other end a rotational center, an arc extinguisher chamber vessel surrounding the stationary contact and the movable contact and defining a pressure accumulating space at one side of an arc generation position at which an electric arc is generated for temporarily storing a pressurized gas pressurized by the arc generated between the stationary and the movable contact upon the current interruption, a main body case including at least one of the arc extinguisher chamber, and an exhaust port disposed at the other end of the arc generation position in the arc extinguisher chamber and the main body case so that the pressurized gas stored within the accumulation space upon the current interruption is exhausted between arc spots formed on the stationary contact and the movable contact.
Also, the arc extinguisher chamber vessel may be constructed in a hexahedron and may have a length c in the direction perpendicular to the plane of rotation of the movable contact, a length b in the direction of initial separation of the movable contact, a length a perpendicular to the b and the c, and may be arranged such that a relation ship a greater than b greater than c holds.
Also, of two spaces defined by dividing a space within the arc extinguisher chamber by a plane passing through the centers of the arc spots formed on the movable contact member and the stationary contact member and perpendicular to a plane of rotational movement of the movable contact member, volume of the space provided with the exhaust port may be arranged to be smaller than the volume of the other space.
Also, the exhaust port may be located in the vicinity of the stationary contact or the movable contact upon separation.
Also, a conductor portion for holding the movable contact member may be disposed within the arc extinguisher compartment so that the movable contact member is rotatable and the pressure accumulation space is defined in the vicinity of the conductor portion.
Also, a flow cross-sectional area for the pressurized gas at the position between the stationary contact and the movable contact in a flow path between the stationary contact and the movable contact from the pressure accumulation space may be made smaller than a flow cross-sectional area for the pressurized gas at the position upstream of the flow cross-sectional area between the stationary contact and the movable contact.
Also, a sidewall of the arc extinguisher compartment vessel in the vicinity of the arc generating position is provided with a chamber having an opening portion in the direction of the arc.
Also, the arc extinguisher chamber vessel may be made of an organic insulating material.
Also, an organic insulating material may be disposed in the vicinity of the arc generating position within the arc extinguishing chamber vessel.
Further, an exhaust port may be provided in the vicinity of at one of the stationary contact or the movable contact upon separation and the organic insulator may be provided in the vicinity of the other of the stationary or movable contact upon separation.
Also, an electrode for the commutation of either one of the arc spots may be disposed in the vicinity of the stationary contact of the stationary contact member or the movable contact of the movable contact member, and the direction of normal of the plane to which the arc spot commutates may be more closely directed toward the exhaust port than is the direction of normal of the plane of the contacting surface of the movable contact or the stationary contact.
Also, a fine opening of the arc extinguisher chamber vessel except for the exhaust port may be closed by a separate member engaged thereto.